The invention lies in the field of actuators and variable length fluid supply means and is directed to improved means for delivering high pressure fluid to a motor mounted on a mechanism which is to be operated at various distances from a base to which it is extensibly connected. It is more particularly directed to such an arrangement in which a hydraulic actuator is used to position the movable mechanism with respect to the base and part of the actuator is used to provide a major portion of the fluid transmission line.
Many machines are in use at the present time in which a massive member of some kind is movably connected to a stationary base and is provided with a fluid motor which may be reciprocating or rotary for performing a specialized function and requires pressurized operating fluid of the order of several thousand pounds per square inch to produce the power necessary for its function. Such machines include large machine tools, cranes, mining machines and others.
In many such installations a servo motor is used which comprises a cylinder mounted on or anchored to a relatively stationary base, a piston slidably mounted in the cylinder for reciprocation by fluid pressure, and a piston rod connected at its inner end to the piston and at its outer end to the load to be moved. The pump or other source of pressurized fluid is usually mounted in fixed position on or adjacent to the base and rigid piping is used to connect the pump to the cylinder to prevent leaks or deterioration in the supply line. Since the fluid motor on the load must be shifted to positions at varying distances from the base it is necessary to provide extensible conduit means for carrying the fluid from the pump or the base to the fluid motor. The conventional conduit means for this purpose are lengths of pipe connected to each other and to the pump and motor by swivel joints, and rubber-like hoses.
Both of these schemes have various disadvantages which render them generally unsatisfactory. The distances involved often approach twenty feet. Two 10-foot pipes with their swivel joints must extend outward in some direction a distance of 10 feet. In many cases that much room is not available. Even when such room is available it is difficult to maintain such slumsy devices in alignment, and the swivel joints rapidly develop leaks. The pipes may be made shorter and more numerous with a corresponding increase in the number of swivel joints. However, such arrangement requires complicated yielding support means for the pipe segments and the joint leakage problem becomes greater.
Flexible hose lines pose similar problems. They must extend outward in some direction when the machine is retracted and they must be yieldably supported. At very high pressures they deteriorate in a relatively short time and are subject to delamination and abrasion damage. Leakage at the connections between hose ends and fittings is also a common problem.